Thermal Insulating Fluids

ABSTRACT

Aqueous and substantially anhydrous fluids having particularly low thermal conductivities and variable densities are disclosed. The fluids include: one or more organic and/or inorganic salts and at least one aprotic polar organic solvent, a mixture of aprotic and protic polar organic solvents, and/or a polar organic solvent having both protic and aprotic polar functional group linkages. The fluids optionally include one or more viscosifying agents and are free of cross-linking agents. Methods for formulating and using the fluids are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims the benefit, and is a divisional application ofprior U.S. application Ser. No. 13/043,033 filed Mar. 8, 2011 entitled“Thermal Insulating Fluids,” which is incorporated herein by referencein its entirety.

BACKGROUND

Fluids are used in a variety of capacities in connection with downholedeep well applications. For example, packer fluids, completion fluids,workover fluids and fracturing fluids, to name a few, each serve acritical role in such applications. The physical and chemical propertiesexhibited by a fluid strongly influence the particular niche for whichthe fluid is most suited. Low thermal conductivity is a particularlyimportant property required of many types of downhole deep wellapplication fluids. Fluids are typically pumped to significant depths indownhole applications where they are exposed to highly elevatedtemperatures. A fluid's favorable thermal conductivity characteristicscan make it an excellent choice for any downhole use in which thermalinsulation is crucial to success of the operation. In addition to lowthermal conductivity, high thermal stability at elevated wellboretemperatures and favorable rheological properties such as a reducedviscosity upon mechanical agitation at ambient temperatures are alsodesired fluid characteristics.

SUMMARY

Embodiments of the invention are directed to thermal insulating fluidshaving particularly low thermal conductivities, variable densities,favorable thermal stability at elevated temperatures, favorablecorrosion and gas hydrate inhibition properties, and relatively highviscosities at elevated temperatures. Embodiments of the invention maybe broadly categorized as being directed to either aqueous thermalinsulating fluids or substantially anhydrous thermal insulating fluids.This categorization is not intended to be limiting but is providedmerely as a means for distinguishing between various embodiments of theinvention.

For the purposes of this disclosure, the terms “thermal insulatingfluid,” “thermally insulative fluid,” “fluid formulation,” “fluid,” and“formulation” may be used interchangeably herein.

To obtain fluids with lower thermal conductivities than aqueous-basedfluids, protic organic solvents such as alcohols and polyols (e.g.,glycols) have recently been used in the formulation of such fluids.Through the addition of halide salts, typically in an aqueous state,high-density fluid formulations using protic organic solvents may beproduced.

The chemical structure of an organic solvent strongly influences itsthermal conductivity characteristics as well as its ability tosolubilize various inorganic and organic salts. Heretofore, theadvantageous use of aprotic polar organic solvents in lieu of, or incombination with, protic organic solvents to prepare fluids withvariable densities and lower thermal conductivities than those preparedwith protic solvents alone has not been recognized. Applicants havedetermined that a wide range of aprotic polar organic solvents are ableto effectively solubilize various inorganic and organic salts. Thesolubilization of these salts permits the formulation of variabledensity fluids suitable for use in HPHT (high pressure, hightemperature) well applications.

The particularly low thermal conductivities achieved by fluids accordingto embodiments of the invention that include aprotic polar organicsolvent(s) and/or polar organic solvents having aprotic functional grouplinkage(s) make them excellent candidates for use as thermal insulatingfluids in wellbore applications. Moreover, until Applicants' invention,the effectiveness with which a wide range of aprotic polar organicsolvents are able to solubilize salts to produce variable density fluidswas unrecognized in the art. As such, not only can variable density, lowthermally conductive fluids according to embodiments of the invention beused in numerous capacities in connection with oil and gas applications(e.g. as insulating fluids, packer fluids, completion fluids, workoverfluids, drilling fluids, and fracturing fluids), but they may also beapplied across a wide range of industries beyond oil and gas.

In a general embodiment of the invention, a thermal insulating fluidcomprises: one or more organic and/or inorganic salts, an aprotic polarorganic solvent, a viscosifying agent, and water. During formulation,the organic and/or inorganic salts may initially be present andintroduced in solid phase and/or in the form of an aqueous brinesolution. Introduction of salts to the thermal insulating fluid providesthe fluid with a suitable density for use as a downhole fluid.

Typically, in this embodiment, only an amount of water sufficient tohydrate or solubilize the viscosifying agent is added to the fluid.Water is not necessary to dissolve the salts because the aprotic polarorganic solvent suitably solubilizes the salts. As a consequence, inthis embodiment and other embodiments of the invention directed toaqueous thermal insulating fluids, the fluid comprises a substantiallyreduced amount of water as compared to conventional aqueous-basedinsulating fluids. As a result, aqueous thermal insulating fluidsaccording to embodiments of the invention are less corrosive thanconventional aqueous-based insulating fluids.

The viscosifying agent may be one or more natural and/or syntheticpolymers. For example, natural polymers such as scerloglucan, syntheticpolymers such as polyacrylic polymers and derivatives thereof, and/orinorganic polymers may be used. In addition, mixtures of polymers aswell as copolymers (i.e. polymers comprising more than one type ofrepeating monomeric unit) may be used such as, for example, mixturesand/or copolymers of acrylic acid and2-acrylamido-2-methylpropanesulfonic acid (referred to as AMPSpolymers). The polymers may include cationic and/or anionic monomericspecies. Moreover, a mixture of one or more polymers and one or moreorganic and/or inorganic salt(s) (e.g. a polycationic polymer containingquaternary ammonium groups in salt form) may be included in thermalinsulating fluids according to embodiments of the invention. Polymers ofvinyl pyrrolidone, polyacrylic derivatives or other polymers may be usedas well. A separate cross-linking agent is generally not required oradded to the polymer(s). That is, fluid formulations in accordance withembodiments of the invention may include one or more viscosifying agentswhile simultaneously being free of a cross-linking agent. Thus, fluidsaccording to embodiments of the invention advantageously possess highlyfavorable thermal conductivity characteristics while avoiding some ofthe problems associated with the use of cross-linking agents such asdifficulties in removing the fluid during workover operations.

In another embodiment of the invention, a thermal insulating fluidcomprises: one or more organic and/or inorganic salts, a mixture of atleast one aprotic polar organic solvent and at least one protic polarorganic solvent, a viscosifying agent, and water. The mixture of aproticand protic polar organic solvents may be formulated in such a mannerthat the ratio of the concentration of aprotic polar organic solvent(s)to the concentration of protic polar organic solvent(s) is at leastabout 1:4 or greater. In a more specific embodiment of the invention,the ratio of the concentration of aprotic polar organic solvent(s) tothe concentration of protic polar organic solvent(s) is in the range ofabout 1:4 to about 4:1. Stated another way, the proportion of aproticpolar organic solvent(s) in the mixture of aprotic and protic polarorganic solvents may be in the range of about 20% to about 80%. However,in other embodiments of the invention, the mixture may be formedaccording to any proportion, including mixtures that include onlyaprotic polar organic solvent(s).

In another embodiment of the invention, a thermal insulating fluidcomprises: one or more organic and/or inorganic salts, at least onepolar organic solvent having one or more protic polar functional grouplinkages and one or more aprotic polar functional group linkages, aviscosifying agent, and water. The polar organic solvent with aproticand protic functional group linkages may be, for example, an alcoholester, an alcohol or polyol ether, and/or an alcohol or polyol amide.

In a more specific embodiment of the invention, a thermal insulatingfluid comprises: one or more organic and/or inorganic salts and at leastone polar organic solvent in which a ratio of aprotic polar functionalgroup linkage(s) to protic polar functional group linkage(s) is at leastabout 1:2 or greater. Stated another way, aprotic polar functional grouplinkages may represent about 33% or greater of all functional grouplinkages in the polar organic solvent. In one or more exemplaryembodiments, diethylene glycol butyl ether may be used as an organicsolvent comprising both aprotic and protic polar functional grouplinkages. However, it should be noted that the organic solvent(s) usedmay include any number of aprotic and protic linkages.

In another more specific embodiment of the invention, a hydrocarbonchain associated with an aprotic functional group linkage in a polarorganic solvent comprises at least three carbon atoms. In an even morespecific embodiment of the invention, the hydrocarbon chain comprises atleast four carbon atoms. For example, in an organic compound comprisingtwo ether linkages and one ester linkage (e.g. R′″—O—R″—O—R′—COO—R), atleast one of R′″, R″, R′, and R may comprise at least three carbonatoms, or in more specific embodiments, at least four carbon atoms.Applicants have determined that polar organic solvents havinghydrocarbon chains comprising at least three carbon atoms exhibitparticularly low thermal conductivity characteristics while still beingable to adequately dissolve salts thereby making them excellent fluidsfor use in connection with oil and gas and other industrialapplications.

As in those embodiments of the invention in which the fluid comprises anaprotic polar organic solvent, embodiments of the invention in which thefluid comprises a mixture of protic and aprotic polar organic solvent(s)and those in which the fluid comprises a polar organic solventcomprising aprotic and protic functional group linkages, the fluid mayfurther comprise a viscosifying agent and water added to the fluid in anamount sufficient to hydrate or solubilize the viscosifying agent. Anyof the polymer(s) and mixtures, derivatives, and combinations thereofmentioned earlier may be used. In addition, the fluid may be free of across-linking agent.

In accordance with one or more embodiments of the invention, any of thefluids previously described may instead be substantially free of addedwater. In those substantially anhydrous embodiments in which the fluidis substantially free of added water, a minimal amount of water may bepresent in the fluid as a result of potential hygroscopiccharacteristics of the salt(s) and/or the solvent(s). A viscosifyingagent may be added to the fluid, or in the alternative, the fluid may befree of a viscosifying agent. A cross-linking agent is not required toobtain suitable viscosification. That is, similarly to the aqueousembodiments, substantially anhydrous fluids according to embodiments ofthe invention may include one or more viscosifying agents while alsobeing free of a cross-linking agent. Any of the polymer(s) and mixtures,derivatives, and combinations thereof mentioned earlier may be used.

Any of the fluid formulations according to embodiments of the inventionmay be free of an ionic liquid. An ionic liquid for the purposes of thisdisclosure shall be defined as a salt in the liquid phase that comprisesonly anions and cations of the salt. Further, fluid formulationsaccording to embodiments of the invention may be solids-free. That is,the fluid formulations may be devoid of any compounds in solid phase.

A method of introducing into a wellbore a fluid according to anyembodiment of the invention is also disclosed. The method comprises:introducing the fluid into the wellbore; and using the fluid as at leastone of: a fracturing fluid, a packer fluid, a completion fluid, adrilling fluid, a workover fluid, and a thermal insulating fluid.

A method for formulating an aqueous thermal insulating fluid isdisclosed. In certain embodiments, the method comprises: slowly adding aviscosifying agent with strong mixing to an aqueous solution comprisingone or more inorganic and/or organic salts. The viscosifying agent maybe, for example, a polyacrylic polymer or a co-polymeric blend. Solidsalt(s) may be added to the mixture along with the viscosifying agent orat a later time. Various additives such as corrosion inhibitors, etc.may be present in the formulation at the time of addition of theviscosifying agent or may be added a later time. The addition of excesswater is generally not required for hydration or solubilization of thepolymer.

The method further comprises adding at least one of: one or more aproticpolar organic solvents, one or more polar organic solvents comprisingaprotic and protic functional group linkages, and a mixture of at leastone aprotic polar organic solvent and at least one protic polar organicsolvent to the formulation and mixing the resulting fluid for at leastabout 45 minutes. Mixing is continued until the fluid is clear. Careshould be taken so as to avoid entrainment of air in the fluid due toexcessively rapid mixing. Additional aprotic and/or protic organicsolvents may be added to the formulation as well. The method isgenerally carried out at ambient temperature and may be modifieddepending on the nature of the polymer(s) and/or the solvent(s) used.

In one or more embodiments of the invention, the mode and order in whichvarious components of the fluid are mixed may be altered. For example,in another embodiment of the invention, a method for formulating anaqueous thermal insulating fluid comprises adding one or moreviscosifying agents to at least one of: one or more aprotic polarorganic solvents, one or more polar organic solvents comprising aproticand protic functional group linkages, and a mixture of at least oneaprotic polar organic solvent and at least one protic polar organicsolvent. The addition of the viscosifying agent(s) may be accompanied bystrong mixing for an extended period of time and may be followed by theaddition of one or more salts in a solid phase or an aqueous saltsolution. The method, and in particular, the mode and order of mixing ispolymer dependent and may be altered depending on the particularformulation being produced.

A method for formulating a substantially anhydrous thermal insulatingfluid is also disclosed. The method comprises dissolving—at an elevatedtemperature—one or more salts in one or more polar organic solventsincluding at least one of: one or more aprotic polar organic solvents,one or more polar organic solvents comprising aprotic and proticfunctional group linkages, and a mixture of at least one aprotic polarorganic solvent and at least one protic polar organic solvent. Themethod further comprises adding one or more viscosifying agents to theformulation. The formulation is mixed strongly both prior to and afterthe addition of the viscosifying agent(s). In certain embodiments of theinvention, the viscosfiying agent(s) is added to the formulation afterthe salt(s) have dissolved and while the formulation is still at anelevated temperature. However, in other embodiments, the mode and orderof mixing may be altered in dependence on the nature of the organicsolvent(s), polymer(s), and/or salt(s) used.

The method for formulating an aqueous thermal insulating fluid and/orthe method for formulating a substantially anhydrous thermal insulatingfluid may, in certain embodiments, further comprise: increasing aconcentration of aprotic polar organic solvent(s) relative to aconcentration of protic polar organic solvent(s) in order to lower thethermal conductivity of the fluid.

These and other embodiments of the invention will be described in moredetail through reference to the following drawings in the detaileddescription that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is table showing the dipole moments and dielectric constants forvarious aprotic and protic compounds.

FIG. 2 is a table providing thermal conductivity measurements for threedifferent fluid formulations comprising ethylene glycol andN-methyl-2-pyrrolidone in varying proportions.

FIG. 3 is a plot of the thermal conductivity of a mixture ofN-methyl-2-pyrrolidone and ethylene glycol as a function of thepercentage of N-methyl-2-pyrrolidone in the mixture.

FIG. 4 is a table illustrating thermal conductivities for various polarorganic fluids with varying numbers of aprotic and protic functionalgroup linkages.

FIG. 5 is a table that illustrates the effect of water on the thermalconductivities of various fluid formulations that compriseN-methyl-2-pyrrolidone.

FIG. 6A is a table providing thermal conductivity measurements atdifferent temperatures for a 12.5 ppg thermal insulating fluidcomprising N-methyl-2-pyrrolidone.

FIG. 6B is a plot of thermal conductivity as a function of temperaturefor the data shown in FIG. 6A.

FIG. 7A is a table that provides fluid viscosity values at various timeintervals for different fluid formulations.

FIG. 7B is a plot of fluid viscosity as a function of time for one ofthe fluid formulations provided in FIG. 7A.

FIG. 8 is a table showing the relative humidity of various protic polarorganic solvents, aprotic polar organic solvents, and polar organicsolvents having both protic and aprotic functional group linkages.

DETAILED DESCRIPTION

One or more embodiments of the invention are directed to aqueous thermalinsulating fluids comprising: one or more organic and/or inorganicsalts, at least one viscosifying agent, and water. In variousembodiments, the fluid further comprises at least one aprotic polarorganic solvent. In other embodiments the fluid comprises a mixture ofaprotic and protic polar organic solvents. In still other embodiments, apolar organic solvent having intramolecular protic and aprotic polarfunctional group linkages is included in the fluid. Embodiments thatrepresent combinations of one or more of the above embodiments are alsowithin the scope of the invention. Further, the fluid may be free of across-linking agent.

One or more alternative embodiments of the invention are directed tosubstantially anhydrous thermal insulating fluids in which the fluidsare substantially free of added water beyond that which may be presentdue to hygroscopic characteristics of the salt(s) and/or solvent(s) inthe fluid. In some embodiments, the substantially anhydrous thermallyinsulating fluid comprises: one or more organic and/or inorganic saltsand at least one aprotic polar organic solvent. In other embodiments,the substantially anhydrous fluid comprises: one or more organic and/orinorganic salts and a mixture of aprotic and protic polar organicsolvents. In still other embodiments, the fluid comprises: one or moreorganic and/or inorganic salt(s) and at least one polar organic solventhaving intramolecular protic and aprotic polar functional grouplinkages. Embodiments that represent combinations of one or more of thesubstantially anhydrous fluids described above are also within the scopeof the invention. Moreover, in some embodiments, the substantiallyanhydrous fluids may be free of an added viscosifying agent, while inother embodiments, a viscosifying agent among any of those previouslydisclosed may be added to the formulation. Substantially anhydrousfluids according to embodiments of the invention may be free of across-linking agent.

As described above, thermal insulating fluids according to embodimentsof the invention comprise one or more organic and/or inorganic saltsdissolved therein. Examples of suitable inorganic salts include halidesof alkali, alkaline earth and transition metals and carboxylatesincluding formates and acetates of alkali, alkaline earth and transitionmetals. The alkali, alkaline earth, and transition metals may beselected from sodium, potassium, calcium, magnesium, aluminum, barium,iron, nickel, cobalt, manganese, zinc and strontium. Specific examplesof suitable salts include, but are not limited to, potassium chloride,sodium chloride, sodium bromide, calcium chloride, calcium bromide, zincbromide, zinc chloride, formates of alkali and alkaline earth metals,acetates of alkali and alkaline earth metals, and mixtures thereof.

In aqueous embodiments of the invention, the salts may be initiallypresent and introduced to the formulation in the form of an aqueousbrine solution. Examples of suitable aqueous brines include brinesformed from any of the salts described above. Alternatively, in thesubstantially anhydrous embodiments, the salt(s) may be added to theformulation in solid phase. Addition of solid salt provides theadvantage of increasing the density of the fluid while minimizing theamount of water in the fluid, which in turn results in a lower thermalconductivity than that of a comparable fluid with a larger amount ofwater.

The degree of polarity of a solvent is generally determined by itselectric dipole moment and its dielectric constant which serve asindicators of the solvent's ability to interact with charged ions orpolar species and to reduce the strength of an electric fieldsurrounding a charged particle that is immersed in the solvent.Applicants have determined that the solubility of salts can be extremelyhigh in a wide range of aprotic polar organic solvents due to theirlarge dipole moments and relatively high dielectric constants.

As previously mentioned, protic polar organic solvents have recentlybeen used in the formulation of thermal insulating fluids. For thepurposes of this disclosure, protic polar organic compounds shallinclude polar organic compounds that contain one or more hydroxylgroups. A hydroxyl group is a protic functional group linkage in which ahydrogen atom is bonded to an oxygen atom. The difference inelectronegativities between the oxygen atom and the hydrogen atom in thehydroxyl group results in a polarization of the hydrogen atom (i.e.development of a partial positive charge at the hydrogen atom). As such,protic compounds readily engage in hydrogen bonding which facilitatestheir ability to solubilize salts.

Aprotic polar organic solvents, however, do not contain any hydroxylgroups, and therefore cannot act as hydrogen atom donors in hydrogenbonding. The solubility of salts in aprotic polar organic solvents is aconsequence of the strong dipoles generated in the solvent molecules bythe separation of partial positive and partial negative charges.

In accordance with embodiments of the invention, aqueous thermalinsulating fluids comprising aprotic polar organic solvent(s) are ableto dissolve salts at ambient temperature during formulation. However,Applicants have determined that substantially anhydrous thermalinsulating fluids comprising aprotic polar organic solvent(s) generallyrequire heating of the solvent(s) during formulation in order toeffectively dissolve the salts. Applicants have further determined thatthe salts remain dissolved in the aprotic polar organic solvent evenafter the solvent is cooled to ambient temperature or temperaturessignificantly lower than ambient temperature. These properties ofaprotic polar organic solvents permit the formulation of variabledensity thermal insulating fluids with thermal conductivities lower(sometimes significantly lower) than those observed with proticsolvents.

FIG. 1 is a table listing several aprotic and protic solvents along withtheir dipole moments and dielectric constants at about 25° C. Theelectric dipole moments are given in units of Debyes while thedielectric constants are dimensionless quantities. Several of theaprotic polar organic solvents listed in FIG. 1 (e.g.N-methyl-pyrrolidone, dimethyl sulfoxide, and N,N-dimethylformamide)possess significantly larger dipole moments than any of the proticsolvents listed in FIG. 1 (e.g. n-butyl alcohol, 2-propanol, ethanol,ethylene glycol). Further, these aprotic polar organic solvents in FIG.1 exhibit higher dielectric constants than the majority of proticsolvents listed. For example, dimethyl sulfoxide—an aprotic polarorganic solvent—has a dipole moment of 4.10 at 25° C. which is largerthan any of the other compounds listed in FIG. 1 and a dielectricconstant of 48.9 at 25° C. which is higher than the dielectric constantsof any of the other protic organic compounds listed.

In certain embodiments of the invention, each of the aprotic polarorganic solvents included in the fluid formulation may have a dipolemoment as measured at 25° C. that is about 2.0 Debyes or larger. Aproticorganic compounds that do not have dipole moments that fall within thisrange, for example, the ester and amine compounds listed in FIG. 1, arenot included in the fluid formulations of these particular embodiments.In certain more specific embodiments of the invention, each of theaprotic polar organic solvents included in the fluid formulation mayhave a dipole moment as measured at 25° C. that is about 2.3 Debyes orlarger.

Aprotic polar organic solvent(s) used in thermal insulating fluidsaccording to various embodiments of the invention may comprise one ormore of the following types of functional group linkages: an amidelinkage, a nitrile linkage, a ketone linkage, an ether linkage, cyclicforms thereof. Further, oligomers, derivatives, mixtures, andcombinations of such compounds may also be used. Specific examples ofsuitable aprotic polar organic solvents include, but are not limited to,acetone, methyl ethyl ketone, cyclohexanone, cyclopentanone,acetonitrile, dimethyl sulfoxide, formamide, dimethylformamide,dimethylacetamide, 2-pyrrolidone, N-methyl-2-pyrrolidone,hexamethylphosphoramide (HMPA), 1,4-dioxane, and tetrahydrofuran.

Thermal conductivity, k, is a measure of a material's ability to conductheat. Thermal conductivity may be measured in the SI units of W/(K*m),or alternatively, in U.S. customary units of BTU/(ft*hr*° F.). Thermalresistivity is the reciprocal of thermal conductivity; therefore, thelower a material's thermal conductivity the higher its thermalresistivity.

Aprotic polar organic solvents generally exhibit considerably lowerthermal conductivities than protic solvents. For example, Applicantshave observed that amides have lower thermal conductivities compared toprotic solvents such as alcohols. For example, the cyclic amideN-methyl-2-pyrrolidone (NMP) with a density of 8.6 lbs/bbl has a thermalconductivity of around 0.09 BTU/ft*hr*° F. as compared to thermalconductivities of 0.16 BTU/ft*hr*° F. and 0.11-0.12 BTU/ft*hr*° F. forthe polyols glycerol and ethylene glycol, respectively, and a thermalconductivity of 0.35 BTU/ft*hr*° F. for water.

One or more embodiments of the invention are directed to thermalinsulating fluids comprising an earth metal halide salt dissolved in anamide-based solvent. Until Applicants' conceived of their invention,conventional wisdom in the art was that amide-based solvents arerelatively less polar compounds, and thus not capable of dissolvingorganic and inorganic salts as readily as aqueous and protic solvents.As such, it was believed that amide-based solvents are not suitable foruse in the formulation of thermal insulating fluids. However, Applicantsdetermined that due to their large dipole moments and relatively highdielectric constants as well as their low thermal conductivities,amide-based solvents are especially effective solvents for dissolvingorganic and inorganic salts, and thus are particularly suited for use ininsulating fluid formulations.

In accordance with embodiments of the invention, use of the salt(s) andorganic solvent(s) may be adjusted and controlled to produce thermalinsulating fluids having favorable thermal and rheological properties.For example, salt may be added to the thermal insulating fluid toincrease the density of the fluid to balance against the pressure of theformation fluid of a well. As such, salt may be added to maintain thedensity of the thermal insulating fluid to within a particular range,typically between about 9.0 to about 18 pounds per gallon (ppg).

As described earlier, both aqueous and substantially anhydrous thermalinsulating fluids according to embodiments of the invention may comprisea mixture of aprotic and protic polar organic solvents. The relativeproportions of aprotic and protic polar organic solvents in the mixturemay be chosen so as to strike an appropriate balance between minimizingthermal conductivity of the fluid and minimizing the cost associatedwith producing the fluid. Low thermally conductive fluids formulatedusing mixture(s) of aprotic and protic polar organic solvents are lessexpensive to produce than those based solely on aprotic polar organicsolvents which are invariably more expensive than protic polar solvents.

According to embodiments of the invention, if a lower thermalconductivity of the fluid is desired, then the proportion of aproticpolar organic solvent(s) in the mixture may be increased. Increasing theproportion of protic polar solvent(s) in the mixture, on the other hand,will generally lower the cost of producing the formulation. These twocompeting considerations may be balanced in dependence on any number ofcriteria including the particular application for which the fluid willbe used, the well conditions, and the necessary specifications of theinsulating fluid.

FIG. 2 is a table demonstrating the effect that an aprotic polar organicsolvent has on the thermal conductivity of a fluid. In particular, FIG.2 provides thermal conductivity measurements for three different fluidformulations, each formulation comprising 14.2 ppg calcium bromide inapproximately the same percentage by volume and the protic polar organicsolvent ethylene glycol and the aprotic polar organic solventN-methyl-2-pyrrolidone (NMP) in varying proportions. As the dataillustrates, formulation 1—which comprises 57% ethylene glycol by volumeand no NMP—has a thermal conductivity of 0.18. Formulation 2—whichcomprises ethylene glycol and NMP in roughly the same percentage byvolume—has a thermal conductivity of 0.17, lower than that offormulation 1. Moreover, formulation 3—which comprises 47% NMP by volumeand no ethylene glycol—has the lowest thermal conductivity of all threeformulations. Thus, the data in FIG. 2 clearly illustrates thatincreasing the amount of the aprotic polar organic solvent NMP in thefluid relative to the amount of the protic solvent ethylene glycolresults in a lower thermal conductivity for the formulation.

Although embodiments of the invention encompass mixtures of aprotic andprotic organic solvents formed in any proportion, Applicants havedetermined that mixtures formulated such that the ratio of theconcentration of aprotic polar organic solvent(s) to the concentrationof protic polar organic solvent(s) is at least about 1:4 or greateryield thermal insulating fluids having particularly low thermalconductivities.

FIG. 3 is a plot of the thermal conductivity of a mixture of NMP andethylene glycol as a function of the percentage of NMP in the mixture.As can be seen, when the percentage of NMP in the mixture reaches about20%, the thermal conductivity of the mixture begins to drop andcontinues to drop considerably until the percentage of NMP in themixture reaches about 80% at which point the thermal conductivity beginsto level off. Thus, increasing the proportion of NMP in the mixture withethylene glycol advantageously yields a substantial reduction in thethermal conductivity of the mixture, particularly when the amount of NMPin the mixture is at or above about 20%. Further, Applicants observedthe unexpected and advantageous result that when the percentage of NMPin the mixture is from about 20% to about 80% particularly low thermalconductivities are obtained. Thus, in accordance with one or moreembodiments of the invention, when the ratio of the concentration ofaprotic polar organic solvent(s) to the concentration of protic polarorganic solvent(s) in the mixture is in the range of about 1:4 to about4:1 or stated differently, when the proportion of aprotic polar organicsolvent(s) in the mixture is in the range of about 20% to about 80%,unexpectedly low thermal conductivities are achieved.

Suitable types of aprotic polar organic compounds for use in mixtures ofaprotic and protic polar organic solvents include any of thosepreviously disclosed. Suitable types of protic polar organic compoundsinclude alcohols, glycols, diols and polyols, glycol mono-ethers,polyglycols, and mixtures or combinations thereof. Specific examples ofprotic polar compounds that may be used include, but are not limited to,ethylene glycol, diethylene glycol, glycerol, ethanolamine,diethanolamine, and triethanolamine.

Various embodiments of the invention are directed to aqueous orsubstantially anhydrous thermal insulating fluids that comprise—inaddition to one or more inorganic and/or organic salts and optionally aviscosifying agent—at least one polar organic solvent having one or moreaprotic and one or more protic functional group linkages. As withmixtures of aprotic and protic polar organic solvents, the presence ofaprotic polar functional groups in the organic solvent lowers thethermal conductivity of the thermal insulating fluid but may beaccompanied by a concomitant increase in the cost of the formulation.

FIG. 4 provides thermal conductivities for various polar organiccompounds comprising different types and numbers of aprotic and proticfunctional group linkages. As FIG. 4 shows, the thermal conductivity ofan insulating fluid that includes an ether functional group linkagediffers from that of the parent alcohol from which the ether is formed.For example, the thermal conductivity of a weighted monobutyl etherderived from diethylene glycol (DEGBE) is 0.09 BTU/ft*hr*° F.representing a 25% decrease from the thermal conductivity observed forits parent diethylene glycol (DEG).

In addition, Applicants have determined—as the data in FIG. 4illustrates—that as the number of aprotic functional group linkages inthe compound increases relative to the number of protic functional grouplinkages, the thermal conductivity of the compound decreases. Forexample, as previously discussed, a monobutyl ether of diethylene glycolwhich includes one alcohol linkage and two ether linkages has a thermalconductivity of 0.09 BTU/ft*hr*° F.-less than the thermal conductivityof diethylene glycol (0.12 BTU/ft*hr*° F.) which has two alcohollinkages and one ether linkage. Moreover, as shown in FIG. 4, thosepurely aprotic polar organic compounds that include several aproticfunctional group linkages and no protic functional group linkagesexhibit particularly low thermal conductivities. For example, dimethylether tetraethyleneglycol which comprises five ether linkages, monobutylether diethylene glycol acetate which comprises an ester linkage and twoether linkages, and diethylene glycol dibenzoate which comprises twoester linkages and one ether linkage each have a thermal conductivity of0.06 BTU/ft*hr*° F. Moreover, cyclohexanone—another purely aprotic polarorganic solvent that comprises a ketone linkage—has a thermalconductivity of 0.05 BTU/ft*hr*° F.

In a specific embodiment of the invention, a hydrocarbon chainassociated with an aprotic functional group linkage in a polar organicsolvent comprises at least three carbon atoms, and optionally at leastfour carbon atoms. For example, in an organic compound comprising twoether linkages and one ester linkage (e.g. R′″—O—R″—O—R′—COO—R), atleast one of R′″, R″, R′, and R may comprise at least three carbonatoms, or in more specific embodiments, at least four carbon atoms. Itshould be noted that any of R′″, R″, R′, and R may represent the sameorganic chain or different organic chains. Applicants have determinedthat polar organic solvents having hydrocarbon chains comprising atleast three carbon atoms exhibit particularly low thermal conductivitycharacteristics while still being able to adequately dissolve saltsthereby making them excellent fluids for use in connection with oil andgas and other industrial applications.

Generally speaking, thermal insulating fluids according to embodimentsof the invention have thermal conductivities that are similar to thethermal conductivities of the one or more polar organic solventsincluded in the formulation. Consequently, polar solvents comprisingaprotic polar functional group linkages are particularly desirable. Aspreviously mentioned, thermal insulating fluids that comprise aproticpolar organic solvent(s) or a mixture of aprotic and protic polarorganic solvents exhibit lower thermal conductivities than fluids formedfrom protic polar solvents alone. Further, as the number of aproticfunctional group linkages within a polar organic solvent increasesrelative to the number of protic functional group linkages, the thermalconductivity of the solvent decreases.

In addition to the trends described above, Applicants have alsorecognized that substantially anhydrous thermal insulating fluidstypically exhibit lower thermal conductivities than aqueous thermalinsulating fluids. As previously stated, anhydrous thermal insulatingfluids according to one or more embodiments of the invention may besubstantially free of added water in excess of any water that salt(s)and/or solvent(s) in the fluid may absorb from the atmosphere due tohygroscopic properties. In one or more embodiments, the only waterpresent in the fluid is that which constitutes an impurity and/or thatwhich is absorbed from the atmosphere. In some embodiments of theinvention, the polar organic solvent in the fluid (e.g. certain aproticpolar organic solvents) may not exhibit hygroscopic properties, and thusthe fluid may be essentially free of water.

FIG. 5 illustrates the effect of water on the thermal conductivities ofvarious thermal insulating fluid formulations comprising NMP. As thedata in FIG. 5 shows, the brine solutions have the highest thermalconductivities (0.29 BTU/ft*hr*° F. for the 11.6 ppg calcium chloridebrine solution and 0.23 BTU/ft*hr*° F. for the 12.5 ppg calcium bromidesolution). The data in FIG. 5 also shows that substantially anhydrousfluid formulations comprising NMP exhibit significantly lower thermalconductivities than corresponding aqueous formulations comprising NMP.For example, 11.6 ppg fluid formulations comprising NMP and zinc bromideand calcium bromide brines, respectively, each have a thermalconductivity of 0.10 BTU/ft*hr*° F. whereas a 11.6 ppg anhydrousformulation comprising NMP and weighted with zinc bromide has a thermalconductivity of 0.085 BTU/ft*hr*° F.

Further, increasing the percentage of salts or brine solution in theformulation has a considerably more pronounced impact on the thermalconductivity of the formulation in the case of aqueous formulations. Asshown in FIG. 5, a 12.5 ppg formulation comprising a calcium bromidebrine and NMP has a thermal conductivity of 0.17 BTU/ft*hr*° F. which issignificantly higher than the thermal conductivity observed for the 11.6ppg aqueous formulations. On the other hand, the 14.7 ppg anhydrous zincbromide based formulation comprising NMP exhibits a thermal conductivityof 0.08 which is less than that observed for the 11.6 ppg anhydrousformulation. This characteristic is particularly advantageous because itallows for formulations comprising aprotic polar organic solvents to beweighted up with salts without an appreciable change in thermalconductivity.

As discussed in detail previously, aprotic polar organic solventsadvantageously exhibit lower thermal conductivities than protic polarorganic solvents while also being capable of dissolving salts aseffectively as protic solvents. Similarly, thermal insulating fluidsformulated from aprotic polar organic solvents according to embodimentsof the invention have lower thermal conductivities as compared to proticsolvent formulations. In addition, the thermal conductivity of acompound generally decreases as the number of aprotic functional grouplinkages in the compound increases relative to the number of proticfunctional group linkages.

Applicants have also determined that the thermal conductivity of anaprotic polar organic solvent decreases as the temperature of thesolvent increases. Thus, downhole fluids that comprise aprotic polarorganic solvents rather than protic polar organic solvents alone exhibitnot only highly favorable thermal conductivities at the hightemperatures encountered in a wellbore environment but alsoadvantageously exhibit a decrease in thermal conductivity as thewellbore temperature increases.

FIG. 6A shows thermal conductivity data at different temperatures for a12.5 ppg fluid formulation comprising NMP. The formulation includes 0.69bbl of 14.2 ppg calcium bromide brine, 0.24 NMP, and 0.075 bbl ofviscosifier. As the data shows, the thermal conductivity of the fluiddecreases from a high measurement of 0.17 BTU/ft*hr*° F. at 72° F. to alow measurement of 0.15 BTU/ft*hr*° F. at 243° F. FIG. 6B is a plot ofthe data shown in FIG. 6A and shows an approximately linear decrease inthermal conductivity with an increase in temperature.

Downhole fluids may encounter convection effects in the wellboreenvironment which can reduce their insulating abilities. Formulatingdownhole fluids with particularly high viscosities in order tocounteract these convection effects is known in the art. However, theespecially low thermal conductivities exhibited by aprotic polar organicsolvent formulations advantageously mitigate the need for fluidformulations having especially high viscosities.

Moreover, thermal insulating fluids comprising an aprotic polar organicsolvent such as NMP demonstrate good thermal stability at high wellboretemperatures. FIG. 7A depicts a table of fluid viscosities at varioustime intervals for different fluid formulations. FIG. 7B is a plot offluid viscosity as a function of time for one of the fluid formulationsprovided in FIG. 7A.

The formulations for which fluid viscosity data is provided in FIG. 7Aeach comprise the aprotic polar organic solvent NMP but differ in theamount of salts, water, and polymer(s) included in the fluid. As shownin FIG. 7A, each of the formulations exhibits a negligible change influid viscosity over time despite the differences in composition. FIG.7B depicts a plot of fluid viscosity values as a function of time forthermal insulating fluid B. Formulation B includes 0.50 bbl NMP, 102.7lbs calcium bromide, 0.42 bbl water, and 7 lbs of viscosifier. The plotin FIG. 7B reflects the data in FIG. 7A showing that Formulation Bundergoes a negligible change in viscosity over the period of one month.

Aprotic polar organic solvents and polymers may strongly bind watermolecules. NMP forms relatively strong bonds with water molecules,whereas other less polar aprotic organic solvents such as ethers withmedium length hydrocarbon groups bind water molecules less strongly. Asa consequence, as with many protic solvents (or polymers), certainaprotic polar organic solvents such as NMP may be used in insulativefluids to inhibit gas hydrate formation.

The ability to bind water is often measured by “water activity”(relative humidity) values using a hygrometer. FIG. 8 shows that theability of NMP to bind water is comparable to that of ethylene glycol, awell-known thermodynamic gas hydrate inhibitor. Diethylene glycolmonobutyl ether—a polar organic compound comprising both aprotic andprotic polar functional group linkages—has a relative humidity of 78%.This demonstrates the poor ability of ether given a combination with aprotic linkage to bind water. Gas hydrate inhibition can be an importantand desirable property of insulating fluids. The added benefit ofcertain aprotic polar organic solvents such as NMP to function as gashydrate inhibitors was unknown in the art until Applicants invention.

Another advantage of aprotic polar organic compounds is that theytypically demonstrate lower corrosivity than protic compounds. Thus,both aqueous and substantially anhydrous thermal insulating fluidscomprising an aprotic polar organic solvent according to embodiments ofthe invention are less corrosive than fluids formed from protic solventsalone. Moreover, aqueous thermal insulating fluids according toembodiments of the invention are also less corrosive than conventionalaqueous fluids because they comprise only a minimal amount of waterneeded to hydrate or solubilize viscosifying agent(s) present in thefluid. The less corrosive nature of aqueous and substantially anhydrousthermal insulating fluids comprising aprotic polar organic solvent(s) isparticularly advantageous when the fluid is used in connection withwellbore environments containing tools, drillpipe, drill casing, and/orproduction tubing that are vulnerable to corrosion. Although corrosioninhibiting chemicals are often added to fluids used in oil and gasapplications, with aprotic formulations according to embodiments of theinvention less of the chemicals are needed.

In various embodiments of the invention, thermal insulating fluidscomprising aprotic polar organic solvent(s) may exhibit a considerablylengthened cool-down time. The cool-down time of a fluid is dependent onboth the thermal conductivity and the viscosity of the fluid and isdirectly correlated to the U value of the fluid which is a measure ofits thermal conductivity over a given distance. Because fluidsformulated in accordance with embodiments of the invention exhibitparticularly low thermal conductivities as compared to conventionalfluids, longer cool-down times are obtainable at lower fluidviscosities.

Thermal insulating fluids according to one or more embodiments of theinvention may comprise one or more additives. The additives may compriseone or more of the following: corrosion inhibitors, bridging agents,sized particulates, buffers, lubricants, breakers, stabilizers,chelants, scale inhibitors, clays, polymers, tackifying agents, gellingagents, co-solvents, viscosity modifiers, wetting agents, fluid losscontrol agents, proppants for use for example in connection withhydraulic fracturing, hydrate inhibitors, oxygen scavengers,surfactants, biocides, emulsifiers and mixtures or combinations thereof.

In other embodiments, the thermal insulating fluid may be essentiallyfree of chemical additives. For example, the thermal insulating fluidmay be essentially or completely free of any additives that may serve toenhance the solubility of the salts in the fluid such as, for example, achelating ligand. Additionally, the fluid may be free of additives usedto stabilize the mixture, such as emulsifying agents. The thermalinsulating fluid may inherently exhibit favorable properties without theintroduction of additional additives. For example, the fluid may beinherently viscous, and thus may not require the introduction ofviscosifying agents or viscosity modifiers. In addition, the fluid maybe free of surfactants.

Insulating fluids according to certain embodiments of the invention mayfurther be free of any other additives that enhance the chemical and/orphysical properties of the fluid. Such additives may include fluid losscontrol agents, bridging agents, sized particulates, buffers, corrosioninhibitors, lubricants, surfactants, breakers, bactericides,cross-linkers, stabilizers, chelants, scale inhibitors, corrosioninhibitors, hydrate inhibitors, clays, polymers, tackifying agents,gelling agents, co-solvents and weight-up agents.

Fluid formulations according to certain embodiments of the invention maybe free of an ionic liquid. An ionic liquid for the purposes of thisdisclosure shall be defined as a salt in the liquid phase that comprisesonly anions and cations of the salt. In addition, fluid formulationsaccording to certain embodiments of the invention may be solids-free.That is, the fluid formulations may be devoid of any compounds in solidphase.

A method for formulating an aqueous thermal insulating fluid isdisclosed. The method comprises: slowly adding a viscosifying agent withstrong mixing to an aqueous solution comprising one or more inorganicand/or organic salts. The viscosifying agent may be, for example, apolyacrylic polymer or a co-polymeric blend. Solid salt(s) may be addedto the mixture along with the viscosifying agent or at a later time.Further, various additives such as corrosion inhibitors, etc. may bepresent in the formulation at the time of addition of the viscosifyingagent or may be added a later time. The addition of excess water isgenerally not required for hydration or solubilization of the polymer.

The method further comprises adding at least one of: one or more aproticpolar organic solvents, one or more polar organic solvents comprisingaprotic and protic functional group linkages, and a mixture of at leastone aprotic polar organic solvent and at least one protic polar organicsolvent to the formulation and mixing the resulting fluid for at leastabout 45 minutes. Mixing is continued until the fluid is clear. Careshould be taken so as to avoid entrainment of air in the fluidformulation due to excessively rapid mixing. Additional aprotic and/orprotic organic solvents may be added to the formulation as well. Themethod is generally carried out at ambient temperature and may bemodified depending on the nature of the polymer(s) and/or the solvent(s)used.

A method for formulating a substantially anhydrous thermal insulatingfluid is also disclosed. The method comprises dissolving—at an elevatedtemperature—one or more salts in one or more polar organic solventsincluding at least one of: one or more aprotic polar organic solvents,one or more polar organic solvents comprising aprotic and proticfunctional group linkages, and a mixture of at least one aprotic polarorganic solvent and at least one protic polar organic solvent. Themethod further comprises adding one or more viscosifying agents to theformulation and cooling the resultant formulation to ambient temperatureor a temperature below ambient temperature.

The method for formulating an aqueous thermal insulating fluid and/orthe method for formulating a substantially anhydrous thermal insulatingfluid may, in certain embodiments, further comprise: increasing aconcentration of aprotic polar organic solvent(s) relative to aconcentration of protic polar organic solvent(s) in order to lower thethermal conductivity of the fluid.

A method of introducing a fluid according to any embodiment of theinvention into a wellbore is also disclosed. The method comprises:introducing the fluid into the wellbore; and using the fluid as at leastone of: a fracturing fluid, a packer fluid, a completion fluid, adrilling fluid, a workover fluid, and a thermal insulating fluid.

As previously disclosed, the particularly low thermal conductivitiesachieved by fluids that include polar organic solvents having aproticfunctional group linkage(s) make them excellent candidates for use asinsulating fluids in wellbore applications. However, given theeffectiveness with which a wide range of aprotic polar organic solventsare able to solubilize salts to produce variable density fluids, lowthermally conductive fluids comprising aprotic polar organic solvent(s)according to embodiments of the invention may be used in numerouscapacities in connection with not only oil and gas applications (e.g. asinsulating fluids, packer fluids, completion fluids, workover fluids andfracturing fluids), but across a wide range of industries beyond oil andgas as well such as, for example, heat traps, insulating fluids,refrigerants, hydraulic fluids, etc.

Furthermore, substantially anhydrous fluids comprising aprotic polarorganic solvent(s) according to embodiments of the invention areparticularly useful in applications requiring fluids that demonstratefavorable thermal conductivity while having minimal water content. Forexample, substantially anhydrous fluids disclosed herein areparticularly useful as fracturing fluids where formation damage by watermight be an issue. Moreover, because substantially anhydrous fluidsdisclosed herein are capable of being weighted up to generate highdensity fluids, such fluids advantageously do not require as muchpressure when being pumped into a wellbore.

While the invention has been described and illustrated in detail withreference to one or more embodiments and modifications thereof, itshould be understood by those skilled in the art that other embodimentsare encompassed within the invention.

What is claimed is:
 1. A fluid formulated to have low thermalconductivity, the fluid comprising a mixture of one or more saltsselected from the group consisting of: an inorganic salt, an organicsalt, and mixtures thereof; and one or more aprotic polar organicsolvents and one or more protic polar solvents, wherein the aproticpolar organic solvents comprise about 20% to about 80% of the mixture ofaprotic polar organic solvents and one or more protic polar organicsolvents such that the ratio of the concentration of the aprotic polarsolvents to the concentration of protic polar organic solvents in themixture is in the range of about 1:4 to about 4:1 in order to lower thethermal conductivity of the mixture, the one or more salts are added inamounts sufficient to maintain the density of the fluid between about9.0 lb/gal to about 18.0 lb/gal, wherein the fluid is substantiallyanhydrous.
 2. The fluid of claim 1, wherein each of the one or moreaprotic polar organic solvents has an electric dipole moment at about25° C. that is about 2.0 Debyes or larger.
 3. The fluid of claim 2,wherein each of the one or more aprotic polar organic solvents comprisesone or more types of aprotic polar functional group linkages, eachaprotic linkage being selected from the group consisting of: an amidelinkage, a nitrile linkage, an ether linkage, a ketone linkage, andcyclic forms thereof.
 4. The fluid of claim 3, wherein at least one ofthe one or more aprotic polar organic solvents comprises a hydrocarbonchain having at least three carbon atoms, the hydrocarbon chain beingassociated with an aprotic functional group linkage.
 5. The fluid ofclaim 4, wherein the hydrocarbon chain comprises at least four carbonatoms.
 6. The fluid of claim 1, wherein the one or more salts areselected from the group consisting of: halides of alkali, alkaline earthand transition metals, formates of alkali, alkaline earth and transitionmetals, acetates of alkali, alkaline earth and transition metals, andcombination or mixtures thereof.
 7. The fluid of claim 1, wherein thefluid is devoid of an amine solvent additive.
 8. The fluid of claim 1,wherein the one or more aprotic polar organic solvents are selected fromthe group consisting of: 2-pyrrolidone, N-methyl-2-pyrrolidone,derivatives of 2-pyrrolidone, dimethyl ether tetraethylene glycol,monobutyl ether diethylene glycol acetate, and diethylene glycoldibenzoate, cyclohexanone, dimethyl sulfoxide, N,N-dimethylformamide,acetone, diethyl ether, acetonitrile, methyl ethyl ketone, and mixturesor combinations thereof.
 9. The fluid of claim 1, further comprising:one or more viscosifying agents; and water sufficient to hydrate orsolubilize the one or more viscosifying agents.
 10. The fluid of claim9, wherein the one or more viscosifying agents are selected from thegroup consisting of: scleroglucan, polyacrylic polymers and derivativesthereof, inorganic polymers, mixtures of acrylic acid and2-acrylamido-2-methylpropanesulfonic acid, co-polymers of acrylic acidand 2-acrylamido-2-methylpropanesulfonic acid, polymers of vinylpyrrolidone, polymers of polyacrylic derivatives, polymers havingcationic monomeric species, polymers having anionic monomeric species, amixture of one or more polymers and one or more salts, and mixtures,combinations, and derivatives thereof.
 11. The fluid of claim 1, whereinthe fluid is free of a cross-linking agent.
 12. The fluid of claim 1,wherein the fluid is introduced into a wellbore for use as at least oneof: a fracturing fluid, an insulating fluid, a packer fluid, acompletion fluid, a workover fluid, and a drilling fluid.
 13. A fluidformulated to have low thermal conductivity, the fluid comprising amixture of: one or more salts selected from the group consisting of: aninorganic salt, an organic salt, and mixtures thereof; and one or moreaprotic polar organic solvents and one or more protic polar solvents,wherein the aprotic polar organic solvents comprise about 20% to about80% of the mixture of aprotic polar organic solvents and one or moreprotic polar organic solvents such that the ratio of the concentrationof the aprotic polar solvents to the concentration of protic polarorganic solvents in the mixture is in the range of about 1:4 to about4:1 to lower the thermal conductivity of the mixture, wherein the fluidis devoid of an amine solvent additive, and wherein the fluid issubstantially anhydrous.
 14. The fluid of claim 13, wherein each of theone or more aprotic polar organic solvents has an electric dipole momentat about 25° C. that is about 2.0 Debyes or larger.
 15. The fluid ofclaim 13, wherein each of the one or more aprotic polar organic solventscomprises one or more types of aprotic polar functional group linkages,each aprotic linkage being selected from the group consisting of: anamide linkage, a nitrile linkage, an ether linkage, a ketone linkage,and cyclic forms thereof.
 16. The fluid of claim 13, wherein the one ormore salts are selected from the group consisting of: halides of alkali,alkaline earth and transition metals, formates of alkali, alkaline earthand transition metals, acetates of alkali, alkaline earth and transitionmetals, and combination or mixtures thereof.
 17. The fluid of claim 13,wherein the one or more aprotic polar organic solvents are selected fromthe group consisting of: 2-pyrrolidone, N-methyl-2-pyrrolidone,derivatives of 2-pyrrolidone, dimethyl ether tetraethylene glycol,monobutyl ether diethylene glycol acetate, and diethylene glycoldibenzoate, cyclohexanone, dimethyl sulfoxide, N,N-dimethylformamide,acetone, diethyl ether, acetonitrile, methyl ethyl ketone, and mixturesor combinations thereof.
 18. The fluid of claim 13, wherein the fluidfurther comprises one or more viscosifying agents, and wherein the oneor more viscosifying agents are selected from the group consisting of:scleroglucan, polyacrylic polymers and derivatives thereof, inorganicpolymers, mixtures of acrylic acid and2-acrylamido-2-methylpropanesulfonic acid, co-polymers of acrylic acidand 2-acrylamido-2-methylpropanesulfonic acid, polymers of vinylpyrrolidone, polymers of polyacrylic derivatives, polymers havingcationic monomeric species, polymers having anionic monomeric species, amixture of one or more polymers and one or more salts, and mixtures,combinations, and derivatives thereof.
 19. The fluid of claim 13,wherein the fluid is free of a cross-linking agent.
 20. The fluid ofclaim 13, wherein the fluid is introduced into a wellbore for use as atleast one of: a fracturing fluid, an insulating fluid, a packer fluid, acompletion fluid, a workover fluid, and a drilling fluid.